6 key processes for new energy vehicle motor manufacturing

The manufacturing of the vehicle body of new energy vehicles is not much different from that of traditional vehicles. Usually, stamping, welding and painting processes and corresponding equipment and conveying devices are still required.

The main change in the general assembly process is the need to arrange the assembly of new components such as batteries, motors, electronic control devices, and high-voltage wiring harnesses, as well as the assembly processes of other electric-driven auto parts such as electric air conditioners and electric power steering systems. and corresponding tooling.

In terms of vehicle inspection, there are obvious differences between the technology and equipment of new energy vehicles and traditional vehicles. Generally speaking, vehicle inspection involves all aspects of automobile main functions and performance inspection. New energy electric vehicles have added the detection of electric drive system and high-voltage electric system, etc., and strengthened the detection of electrical performance and electrical safety.

The key manufacturing technology of electric vehicle powertrain is mainly reflected in the manufacture of electric motor system, battery system and electronic control system. Compared with conventional vehicles, the process changes in the assembly line of electric vehicles are most prominent. In electric vehicles, the motor system involves the manufacture of components such as motor control system, mechanical deceleration and transmission, as well as the assembly process of battery modules and battery packs.

Key technical requirements for motor manufacturing process

The technical and economic indicators of electric motors are largely related to their manufacturing materials and manufacturing processes. In the motor manufacturing plant, the quality of products made of the same design structure and the same batch of raw materials often varies greatly. Without advanced manufacturing technology, it is difficult to produce advanced products.

Those key processes in motor manufacturing.

1. Stator core

1.1 The requirements for punching sheets are as follows:

The punched sheet shall meet the dimensional tolerance specified in the drawings.

The punched surface should be smooth and uniform in thickness. Stator and rotor punching burr ≤ 0.05mm.

The coaxiality between the inner circle or central hole and the outer circle of the punched sheet: Φ0.04 ~ 0.06mm for one punching of the inner and outer circles, and the appropriate relaxation for two punches of the inner and outer circles.

The unevenness of the groove tooth distribution of the punching sheet, that is, the difference between the maximum and minimum tooth width is 3 or 4 grades.

The center line of the groove should pass through the center of the circle, and there should be no obvious skew.

The insulating layer on the surface of the stamping sheet should be thin and uniform, and have sufficient dielectric, oil-resistant, and moisture-proof properties.

The number of punches with missing edges shall not exceed 2%, and the height of the missing edges shall not exceed 20% of the height of the yoke.

1.2 The requirements for stamping lamination are as follows:

The task of iron core pressing is to arrange and compress a certain number of punched sheets into a compact and suitable whole with accurate size and neat appearance.

The iron core weight or lamination factor must comply with the drawings. Insufficient core weight will increase the magnetic induction intensity, resulting in increased iron consumption of the motor, increased excitation current, and reduced power factor and efficiency.

The pressure should be uniform and the tightness should be appropriate. The iron core should not be loosened or deformed under the comprehensive action of mechanical vibration, electromagnetism and heat. If the iron core is too loose, the number of punched pieces in a certain length will be reduced, not only the magnetic cross-section is insufficient, but also cause vibration noise and damage the insulation; Consumption increased dramatically. If the pressure is uneven, the insulation is easily damaged if it is too tight, and the iron core is often loosened if it is too loose.

2. Cast aluminum rotor

Surface quality requirements:

There must be no cracks in the end rings, fan blades and balance columns.

The size and depth of the shrinkage cavity on the surface of the end ring shall be less than 20% of the height of the end ring, and the maximum shall not be greater than 3mm, and only one cavity is allowed at each end.

Wind blades and sharp corner defects should be less than 3mm.

Check for defects such as broken strips, cracks, pores, porosity and shrinkage cavities.

3. Winding

The winding is the key component of the motor, and it is also the weakest link that is most vulnerable to damage. It is affected by electromagnetic, thermal, mechanical vibration, and environmental factors. Motor life, operational reliability mainly depends on the winding.

3.1 Coil manufacturing technical requirements:

The wire diameter and number of turns of the winding should be accurate. There should be no more than one joint for each coil, no more than two joints for each phase coil, and no more than four joints for each coil.

The size is suitable and meets the requirements, guaranteed by the winding die.

The coils should be arranged neatly, not crossed, and the insulation should not be damaged. The inter-turn and ground insulation of multi-turn coils should be good and reliable.

3.2 Technical requirements for winding embedding, shaping and wiring:

Check and clean the iron core before embedding wires. If there are protruding parts on the surface of the stator and in the groove, they must be filed and blown clean (not in the wire embedding area).

The winding pitch (slot pitch), the wires between the coils, and the relative positions of the lead wires must be correct.

Winding slot insulation, layer insulation, phase insulation should be good and reliable. The quality and structure size of the insulating material shall comply with the regulations.

The surface of the slot wedge should be flat and smooth, and the winding insulation should not be damaged when inserted. Windings, insulation, and slot wedges should be symmetrical in length at both ends of the stator core.

The wires at the end of the winding should be arranged neatly without serious crossing. End binding and insulation shall meet the requirements.

Do not use metal tools to directly contact the winding when inserting wires and shaping, and do not use excessive force to avoid damage to the insulation.

3.3 Technical requirements for winding varnish drying:

Pre-baking, dipping, drying process parameters, insulation resistance should meet the specified requirements.

The dipping paint is uniform and transparent, without impurities and lumpy substances, and without deterioration. The viscosity of the paint should meet the process requirements.

After drying, the color of the paint film on the surface of the winding should be uniform. The paint film should be non-sticky and slightly elastic when touched by hands. There should be no cracks and wrinkles on the surface. No wedge misalignment.

4. Base

The dimensional tolerance and roughness of each processing part shall comply with the drawings.

The shape and position tolerances of each processing surface shall comply with the drawings. Among them, the coaxiality between the spigots at both ends and the inner circle, and the jump of the two ends facing the axis of the spigots are the key points for machine base processing. There should be proper tightness between the inner circle and the iron core to ensure that the stator core does not loosen or move in series during the operation of the motor.

5. End cap

The rigidity of the end cover structure, the dimensional accuracy and shape deviation of the seam and the bearing chamber will affect the uniformity of the air gap between the stator and the rotor. Care should be taken during design and processing.

6. Motor shaft

The core gear diameter, bearing gear diameter and roughness of the rotating shaft, the outer diameter and roughness of the rotor core, the distance between the bearing gears at both ends, and the coaxiality between the outer circle of the core and the shaft are all key to processing. There should be appropriate tightness for the shaft, iron core and fan blades to ensure that the rotor core and fan blades do not loosen or move in series during the operation of the motor. In addition, the dimensional tolerances of shaft extension and keyway should meet the requirements of relevant product standards for installation dimensional tolerances.